The present invention relates in general to grinding machines and more in particular to machines known as surface grinders and adapted to grind accurately finished surfaces on parts of various sizes and shapes such as may be held by suitable chucks or work holders during the grinding operation.

My improved grinding machine is characterized by a horizontal bed on which one or more work supports may be mounted, a vertical column extending upward from the bed, a master bearing member rotatably and slidably supported on the column and carrying in balanced relation a grinding wheel assembly on one side and a driving motor On the opposite side, and mechanism for raising and lowering the bearing member on the column in order to adjust the grinding wheel relative to the work.

The object of the invention is to provide a new and improved grinding machine of the foregoing type.

A special feature of the invention is an automatic control arrangement for performing a predetermined grinding cycle on a part held by a rotatable work support, the arrangement including an automatic feed for the grinding wheel and automatic latching and releasing mechanism for the grinding wheel assembly which maintains it in operative relation to the work during a grinding cycle and restores it to a non-interfering position at the end of the grinding cycle to enable the operator to remove the finished work piece and replace it with the next piece to .be ground.

The foregoing and other features are described in detail hereinafter, reference being made to the accompanying drawings, in which- Fig. 1 is a front elevation of a grinding machine embodying the invention, including a section through the base and certain other parts on the line ll-|, of Fig. 2, and a section through the rotatable work support on the line I, Fig. 2;

Fig. 2 is a section on the line 22, Fig. l, and is essentially a top or plan view of the machine;

Fig. 3 shows a cam which forms part of the automatic feed mechanism;

Fig. 4 is a section through the master bearing member on the line 4-4, Fig. 1;

Fig. 5 shows a latch mechanism which is part of the automatic control;

Fig. 6 is a partial section on an enlarged scale on the line 66, of Fig. 2;

Fig. 8 is an enlarged view of the micrometer indicator and part of the micrometer dial; and

Fig. 9 is a view of the work rotating mechanism as seen from the right in Fig. 1.

Referring to the drawings, the reference character I0 indicates a circular base having an upwardly extending rim I l. The rim has an annular interior recess for receiving the large flanged ring l2, the two forming a reservoir for coolant. An overflow pipe I3 serves to drain the coolant into a sump (not shown) in the subbase I l. The circulating system for coolant may be of known character and has been omitted in order not to complicate the drawings.

The subbase is preferably rectangular in horizontal section and rests on the floor or other support for the machine. It is flanged at the top where it supports the base Hi. The base may be secured to the subbase by means of countersunk screws such as I5. The base and subbase may be iron or steel castings, and the former preferably has an accurately finished horizontal interior surface It on which work holding chucks or other devices may be mounted. A known form of magnetic chuck I1 is shown in Fig. 2.

The base [0 has an opening at the center thereof, surrounded by an annular recess. The hollow vertical column [8 has a flange at the bottom which rests in this recess. The column is secured in position by screws such as [9 which pass through the flange and are threaded into the base. The upper portion of the column I8 is somewhat reduced in diameter and has a finished exterior surface for reception of the master bearing member 20.

The bearing member 20 is seen in elevation in Fig. 1 and in horizontal section in Fig. 4. It comprises a casting having finished interior bearing surfaces engaging the exterior surface of the column I8. The inside diameter of the bearing member is enlarged for some distance about midway between its upper and lower ends to provide an annular space 2| which is packed with grease. The left hand wall of the bearing member is divided by a vertical slot 22, Fig. 4, which is filled by a compressible strip 23 of wood or other suitable material to prevent the escape of grease. The

vertical slot 22 is bridged by three cap screws such as 24 by means of which the bearing member may be. adjusted to a very close fit on the column 18. These screws also afford means for taking up wear; if any occurs.

For the major portion of its length downward from the top the bearing member 20 is square in cross section. From a point just below the lower cap screw 24, however, the bearing member is round, forming a shoulder indicated at 25, Fig. 1. The rounded portion of the bearing memher is indicated at 26. The plate 21, seen also in Fig. 2, has an opening for the rounded part 2G 01' the bearing member and rests against the shoulder 25, where it is secured at the four corners of the bearing member by screws such as 29. The late l l extends to theright nearly as far as inner w n or ring,- where itsupiports th'e' curved apron tr guard as. The handle 30 is provided for use by the operator in rotating the bearing member and part supported thereby on the column l8, as will be explained herein after.

The reference character 4| indicats a Wm!- drical guard which is secured to the rounded lower end 26 of the bearing member 20 by screws such as 42 and extends downward around the column I8 as shown.

The reference character 1| indicates showing for thegrinding. wheel spindle and i shown, in 8.11 also in dotted lines in Fig. 2. The housing is rectangular in cross sectionand is provided with vertical flanges, such as 32 through which cap screws suchas 33.extend,to clamp the housingto the bearing member 28. 'I'heupper end ol the housing is shown in section in Fig. 6, from which it yvlllbe seen that thehousing is pivotally supportei betore the screws 33 are tightened, on the. stud 34 the base of which is fixed in a hole hijhe bearing member 2,9. The holes in the flanges 31 thr ough which the screws 33 pass are slightly larger than the screws, which makes it pos ible to adiustthehousin about the stud 34 aq a .pivotjo align the grinding wheel spindle wi ht cco wmnifl. .l '1fhe hollowspindle in cated at 35, Fig. 6, rotatably mounted in a vertical channel Q5 inhousing 31 by means of theball bearing 31 at the top and vor re or more ball bearings (not at the lower end of channel 36. The mannel is closedabove bearing 31 by means of thesrqared c n i landme flan ed olla 3.9. the latter havinsa pr es s ,nt on the spindle 35 and helm. rotata le he ew th. The pulley is suitab s c d, n. t es ind e 3 shits upper n t ia q er and the s ndlecarri s the rind- 1 8., Pineal h ch.can he s nin ig.1. he

of the member 46 which turn is slidably e eled. 9. the mu i 3 I 'Iham m e m fidii d e at yato. th m s n I y a a {time a ran emen p t d h han e 1 in rdertor ai sethe guard 45 as the grinding wheel 44 wears away. The details are not shown they form no part oithe invention. It will noted that. the, plate 21 has an opening for the guard 45 and the grinding wheel 44. Tne motor. is mounted on thebearin mem ber il qpposite thejhousing 3|. ,Themo'unting Arrangement comprises a plate 5|, Fig. 4, to whichthe base of the motor is attached, and a bracket 52 which is suitably secured to the bearing member 20. The plate and bracketare proyided with operlapping ears throughwhich holes 'arejdrilled to receive the pivot rod 53. A pulley I4 is mounted on the motor shaft "and is connected with the pulley 43, on.the grinding wh'eel spindle byy belts 5 5 and S6. The belts are shown in dotted lines in Fig. 1 and also appear in-Fig. 76 ward movement of 4 6. They pull the motor and mounting plate ll toward the bearing member 20 and against a stop 51, comprising a stud 51 which is threaded into the bearing member. This stud aflords means for adjusting the tension 01' the belts.

The mechanism for adjusting the bearing member 20 vertically on the column l8 includes the flanged nut 60 and the micrometer screw ll. shown in Fig. 6. The upper portion of the nut estates through a ml in th' cl'r'cdar plate 02 whim rests against the flange on the nut and is rigidly secured thereto by means of screws such as 63. The plate 62 is positioned in a recess at thqtop pf the bearing member 28, where it is secured by screws such as 64. Thus the nut BI is firmly attached to the bearing member 20.

micrometer screw 6| is threaded in the nut 60 extending for some distance above and below the same in the position in which the parts are shown, and is provided with a thrust bearing 65 at its lower end. The bearing is supported on the disc or ring 65, and the latter normally rests on the shoulder 61 of the interior wallofthe hollow column l8, 7 The shoulder is formed by enlargement of the bore of the column which extends a short distance down from thetopal shown. As will be explained presently.- the disc 66 may be raised off the shoulder 61(as it is shown in thedrawing) and lowered thereto by csn qf het b la m be I The micrometer screw 6] is rotated by megnl of the hand wheel 10, seen best in Fig. 2. The hand, wheel has arim of large diameter, which enables it to be reachedeasily by the operator. and acentralhubjl to which the rim is connected by spokes as shown. The hub 1| is secured to the top of the tubular member 12 which surround the upper portion of the micrometer screw II and is provided with a flange 18 at its lower end. The micrometer dial is indicated at 14 andhasa central hub 15 which fits over the member 12 and rests, against. the top of the flange 18; Beneath the flange 18 there is a split ring 16 which lies partly in a groove formed in the nut 68 near the upper end thereof; being rotatable on the nut. The parts are held together by means 01' mm suchas 11 and 18 which pass through holes in the hub ,15'and name: 18 and are threaded into the ring 16. Summing up the foregoing, it will be seen that the hand wheel 18 and the micrometer dial 15 are rigidly connected by means of the tubular member 1! and that these parts are rotatably mounted on the nut 60 (and thereby on the hearing member 20) by means of the split ring 10. This ring may be made in two overlapping sections so'that it can be assembled in the gm" m the nut 60.

The driving connection between the hand wheel and the'mic'rometer screw 8| comprises two key: 88 and 81, shown in dotted lines in Fig. 2. The key '80 is also seen in Fig. 6. These keys are fixed in slots or kyways in the tubular member 12 and are slidable in keyways such as 82 in the microme'ter screw Bl. As we are shown in 6, the keys extend downward about half way into the k'eyways s2. Rotation oi the hand wheel rotates the micrometer screw 61 in the not Ill and raises or lowers the bearing member 10 on the column I8, dependmg on the direction of rotation, the keys to and 84 sliding in the keyways 82 during such movement. In its lower most position the lower end or the bearing member engages the shoulder ll, Fig. 1, on the column I 8. No stopi's necessary to limit their]:-

the bearing member. It'mlw be noted, however, that the keys an and 8| will leave the keyways 82 in the micrometer screw before the screw can be turned downward clear through the nut, which makes further rotation of the hand wheel in this direction ineffective and accordingly limits the distance through which the bearing member may be raised by rotation of the handwheel.

It may appear that rotation of the hand wheel would have a tendency to rotate the bearing member 20'and all associated parts about the column I8, the entire assembly being supported on the thrust bearing 65. It is indeed possible to accomplish this by a very careful and gradual application of force to the hand wheel. In the normal operation of the hand wheel, however, the hand wheel rotates relative to the bearing member and turns the micrometer screw 6| in nut 60 as described, due partly to the friction between the bearing member 29 and column I8 and partly to the great inertia of the bearing member and the heavy parts supported thereon. When the hearing member assembly is rotated in the course of the operation of the machine, by means of handle 30, for example, the entire assembly including the hand wheel and micrometer dial rotates as a unit, on the thrust bearing 55.

The plate 84 extends over the motor 50 and housing 3| and is attached to the top of the bearing members 20 by means of countersunk screws. It will be appreciated that since the plate 62 is circular there is ample room at the four corners of the bearing member for these screws. The plate 84 has openings therein for the motor shaft, the micrometer screw 6| and parts associated therewith, and the spindle 35. These openings are indicated in Fig. 6, except the opening for the motor shaft.

The belt guard 85 is shown in Figs. 1 and 2. This guard encloses the belts 55 and 56 and rests on the plate 84 to which it is secured by screws such as 80, Fig. 6. The guard is notched in front and rear for the micrometer dial 14, which extends outside the guard, and has an opening at the top for the tubular member I2 which supports the hand wheel I above the guard. The threaded nipple 81 is mounted on the guard as shown in Fig. 6 and is part of the circulating system for supplying coolant to the hollow spindle 35 which carries the grinding wheel 44.

The micrometer dial I4 is calibrated on its periphery and cooperates with an index member 88 which is mounted on the guard 85. This index member and part of the dial are shown on an enlarged scale in Fig. 8. The scale divisions on the dial are properly related to the pitch of the micrometer screw 6|. The pitch of the screw may be 20 threads to the inch, for example, so that one complete rotation of the hand wheel will raise or lower the bearing member assembly /20 or .050 of an inch. The micrometer dial may then have 50 scale divisions, each corresponding to a movement of .001 of an inch. The dial is relatively large and the scale divisions are far apart so that each division could be divided into smaller divisions, each corresponding to .0001 of an inch. It is preferable, however, to place these finer scale divisions on the index member 88. as shown in Fig. 8.

It may be noted at this point that the driving connection between the hand wheel I0 and the micrometer screw 6| is substantially direct, the only relatively movable parts being the parts included in the sliding connection with the screw. The keys 80 and 8| are carefully fitted to the keyways in the screw to eliminate play and the backlash as read on the micrometer dial does not exceed about .0002 of an inch.

The rotatable work support may be of any suitable construction, depending on the nature of the parts to be ground. It may have a. chuck or collet, for example, for holding the parts. As shown herein, however, the work support is relatively simple, being adapted to support circular spacers or washers such as 90, and comprises a housing 9| and a flanged shaft 92 rotatably supported therein by means of bearings 93 and 94. The lower end of the housing 9| extends through an opening in the base I0 and a flange on the housing is received in an annular recess surrounding the opening, where it is secured by screws as indicated. The side wall of the subbase I4 is cut away beneath the opening in the base I0 to provide room for the lower end of the housing 9| and shaft 92 and for the pulley 95 which is secured to the lower end of the shaft by the nut 96. As its upper end the shaft 92 has an accurately finished horizontal surface for supporting the work piece 90, which as previously mentioned may be a spacer or washer, which is to be ground to the required thickness. spacer and other similar spacers to be ground may conveniently be provided with two small. holes for receiving two pins which project upward from the finished surface at the end of the shaft. The reference character 91 indicates a guard which is provided to protect the bearing 93 against the entrance of dust and debris produced by the grinding operation.

The driving motor for the work support is indicated at I00 in Figs. 1 and 9. The motor is supported on the housing IOI which contains speed reducing gears for connecting the motor shaft with the output shaft I02. The housing |8I is secured to the wall of the subbase I4 in the proper position as shown in Fig. 1. A pulley I04 is mounted on shaft I02. The belt I03 is carried on pulleys I04 and 95 and serves to connect the shaft I02 with the shaft 92.

The mechanism for raising and lowering the bearing member 20 and associated parts on the column I8 during an automatic grinding cycle includes the tubular member 68, also referred to as the elevating sleeve. This sleeve is contained within the hollow column I8 and has bearings above and Ibelow on the interior wall of the column in which it is slidable vertically. The sleeve 88 is closed at the lower end by the plate or disc I05.

The elevating lever I09 is pivoted on the bracket I0'I which has a threaded extension by means of which it is fastened to the base ID. The lever I09 may be bifurcated or slotted at the ends for reception of the flattened end of bracket I07 at the right and the roller or follower H0 at the left, also the roller I08 which is engaged by the closure plate I06 of the elevating sleeve 68. The roller I08 is located only a short distance to the left of bracket IN, the ratio of the long arm of the lever to the short arm being about 3 to 1.

The driving motor for the elevating mechanism is indicated at I I2. This motor is supported on the housing I I3 which is attached to the wall of the subbase I4 as shown. The housing 3 contains speed reducing gears for connecting the shaft of motor II2 with the output shaft M4 to drive the latter at a slow speed, which may be, for example, about 2 rotations per minute. The cam II6, shown on an enlarged scale in Fig. 3;

This

7 ismmmtedcnthematt il4andcooperatuwith roller ileforopenting the lever I50. Thchcusing I I1. supported on the wall of'subbase I4, cm.- tains a normally open switch which is operated wean III byrnemofalevermechanism in during each rotation of the shaft I.

AsshownmFig.2,thereisasprmg I2lwhich normally holds the edse of the apron 20 against the stop III. In this position, thebearing member assembly including the grinding wheel 44 is rotated about 30 degrees in a counterclockwise direction from the positim in which it is shown in Fig. 2. This leaves the rotatable work support 02 fully exposed and accessible to the operator.

When the operator rotates the bearing member assembly in a clockwise direction by means of thehandle 20 to the position in which it is shown in Fig. 2, it becmnes locked by a latching mechanism. This mechanism is partly enclosed in a homing I22 secured to the flanged upper rim of ring I2 and is so oriented that when the bearing member is in latched position the path of the grinding wheel 44 is directly above the center of the shaft 92 and the work piece 90 supported thereon.

Details of the latching mechanism are shown in Pig. 5. It comprises a frame I23 secured to the ring I2, a latch I24 which is pivotally mounted on the frame, and a catch I25 attached to the apron 25 and adapted to cooperate with the latch I24 as shown to hold the assembly in position a ainst the pull of spring I20. It will be noted that the latch I24 is urged into operative engagement with the catch I25 by the spring I26. The solenoid I20 is mounted on frame I23 and is adapted,- when energized, to rotate latch I24 on its pivot to release the catch I25. This permits the grinding wheel assembly to be rotated by the spring I20 until its movement is arrested by the stop I2I. When the solenoid I20 is deenergized, the ensuing rotation of the latch I24 by the spring I25 causes it to engage the operating member I29 of a normally closed switch I21 and open it. These operations will be explained more fully in connection with Fig. '7.

Referring now to Fig. 7, the reference character 8 indicates the main switch, through which three-phase alternating current is supplied to the conductors I4I, I42 and I43 and thence to the motors =50, I and H2 under control of relays I44 and I45. These relays may Ibfi of any suitable construction, adapted to operate on alternating current, and are shown in conventional manner. The switches SI and S2 are stop and start switches, respectively, and are also shown conventionally. Other parts shown in the circuit drawlng have already been described.

It will be understood that the switches SI and S2 may be mounted in suitable manner on the base of the machine, where they will be convenient to the operator. These switches and the wiring are not shown in the mechanical drawings. Fig. 1 does, however, show the conduits I50 and II for the conductors I55 which supply current to the motor 50. The conduit I50 is supported on the base III by a clamp I52 and on the flanged ring I2 by the bracket I53. The conduit ISI is supported on the plate 84 by a holding device I54. The upper ends of the conduits are above the center of column I 8 and are spaced apart for a short distance, where the conductors I55 are unconfined. These conductors are flexible and the arrangement thus provides for about 8 I 180 degree rotation of the grinding wheel assembly about the column It It will be appreciated, however, that the machine is inherently adapted for contimrws rotation of the grinding wheel assembly about column I5.

The operation of the machine will now be explained, it being assumed for this purpose that the machine is to be used for grinding finished surfaces on spacers such as 50. Some preliminary adjustments which have to be made on setting up the machine will first be explained.

The cam I" is designed in accordance with the particular grinding Job to be performed, although of course a given cam may be used on different jobs if conditions permit. Several cams may be provided and are readily interchangeable. In the present case it may be assumed that the maximum amount of material which has to be removed on any spacer to reduce it to the required thickness is about .030 of an inch. The total lift of the grinding wheel should then be about .050 of an inch, in order to aflord the necessary clearance between the work and the wheel as the latter is moved to grinding position. The total rise on the cam should be suflicient to produce the indicated lift 01' the grinding wheel plus an additional amount which is necessary in order to insure that during the spark out period the thrust bearing 55 will be supported on the shoulder 51 in column I8 rather than on the cam. It is preferable to allow about .005 of an inch clearance between the roller I00 and the plate I 06 when the cam follower H0 is resting on the spark out section of the cam in order to insure that the above condition will obtain.

Since the roller I00 is located in the subbase where it is not very accessible the clearance may be measured by means of a thickness gauge inserted between the cam and the follower IIO, making due allowance for the difference in the length of the lever arms of lever I00. If the cam is not in the proper position, the machine is started in the manner more fully described hereinafter and is stopped when the spark out section of the cam comes into engagement with the follower. The clearance is then measured and if any adjustment is required it is accomplished by raising or lowering the housing II3 on the subbase I4. The housing is secured to the subbase by cap screws which extend through slots in the flanges or feet of the housing which rest against the subbase so that the adjustment can be made as described.

The grinding wheel is adjusted relative to the work with the cam follower IIO restin on the dwell section of the cam, as it is shown in Fig. 1. With the parts in this position, and with a work piece or spacer on the work support 92, the grinding wheel is lowered by means of the hand wheel 10 until it clears the top of the spacer 90 by about .020 of an inch. The grinding wheel assembly should be in latched position above the work support while the adjustment is being made and after it is completed the latch I24 can be released by hand to permit restoration of the grinding wheel to normal position with the edge of apron 28 against the stop I2I. It will be understood that the adjustment of the grinding wheel as well as the adjustment of the cam is made with the main switch open and the motors inactive, the power bein applied only to rotate the cam to the proper position when necessary.

The machine being ready, the operator starts grinding operations by closing the main switch S again, after which he operates the start switch S2 momentarily and then rotates the grinding wheel assembly to grinding position by means of the handle 30, where it is held by the latch I24. The closure of the main switch supplies current to the conductors I 4|, I42 and I43. The operation of the start switch closes a circuit for relay I45 in an obvious manner, bridging the relay across the conductors II and I43. Upon energizing, relay I45 establishes a holding circuit for itself at contact I46 and at its three upper contacts it extends the three conductors I4I, I42 and I43 through to the motor 50, which starts to run and rotate the grinding wheel 44.

When the catch I25 becomes locked by the latch I2 3, the latter is rotated sufiiciently to permit the switch I21 to close, thereby establishing a circuit for relay I44. Upon energizing, relay I44 closes the three conductors I4I, I42 and I43 through to the motors I59 and I I2 and these motors begin to run. Motor I rotates the shaft or work sup-port 92 and the work piece, spacer 90, which is supported thereon. Motor II2 rotates the shaft H4 and the cams II 5 and H6.

In response to rotation of the cam I IS, the cam follower Ht leaves the dwell section of the cam and passes on to the rapid feed section, causing the grinding wheel to be quickly lowered into engagement with the work piece 90. This is accomplished by the lever I09 and the elevating sleeve 68. Grinding now begins and continues as the grinding wheel is gradually lowered by cooperation of the cam follower with the slow feed section of the cam. Shortly before the end of this section of the cam is reached the ring 66 supporting the thrust bearing 55 comes to rest on the shoulder 51, which prevents further lowering of the grinding wheel. The cam rotates freely during the spark out period, therefore, while the grinding wheel cooperates with the rotating work sup-port to produce a finished surface on the work piece 98.

At the end of the spark out period, the cam follower comes into engagement with the wheel rise section of the cam, causing the grinding wheel to be raised off the work piece by means of lever I89 and the elevating sleeve 68. When the cam follower reaches the dwell section of the cam Ilfi, the cam H5 closes the switch II1, thereby closing a circuit for the solenoid I28. Upon energizing, solenoid I28 rotates the latch I24 to release the catch I25, whereupon the grinding wheel assembly is rotated on the column I8 by the spring I28 until its movement is arrested by the stop I2 I. The continued rotation of cam I I5 now permits the switch II1 to open, deenergizing the solenoid I28. This takes place while th cam follower I I9 is still in engagement with the dwell section of cam I i6, Upon deenergization of solenoid I28, the spring I26 rotates the latch I24 to open the switch I21, whereupon the relay I44 deenergizes and stops the motors I00 and I I2. This completes the grinding cycle.

The operator may now remove the spacer 90 from the work support and measure it with a micrometer to determine if its thickness is correct, or within the tolerance limits assigned. Being the first piece ground, it may not be exactly right, so that adjustment of the grinding wheel is necessary. This can be done very accurately by means or the hand wheel 10 while reading the amount by which the grinding wheel is raised or lowered on the micrometer dial 14 and the associated index member 88.

Another s cer u h as ow be place in position on the work support 92, after which the grinding wheel assembly is again rotated to grinding position by the handle 30. The grindin wheel becomes latched in this position as before and the operation of the latch I24 closes the switch I21 to energize relay I44 and start the next grinding cycle.

It will be noted that the work supporting surface on shaft 92 and the shoulder 61 on column I8 are fixed as regards their relative elevation, so that the only variable which can affect the thickness of the finished spacers is the gradual wearing away of the grinding wheel. The operator takes this factor into consideration by measuring the finished spacers from time to time as they are removed from the work support and by lowering the grinding wheel when necessary.

During grinding operations as described the motor 50 continues to run. If it should become necessary to stop the motor for any reason, this can be done by operating the stop switch SI to open the holding circuit of relay I45. In an emergency the stop switch may also be used during a grinding cycle to stop the other motors.

The grinding machine is adapted for use as a hand operated machine for grinding work pieces supported on the magnetic chuck I1, or on other work supports arranged on the surface I6 of the base I0. In order to prepare the machine for this type of grinding operation without preventing the relatively quick resumption of the grinding operations such as previously described, the machine may be stopped with the cam follower III] on the spark out section of the cam I I6 so that the thrust bearing 65 is supported on the shoulder 61. The spring I20 is then unhooked at the apron 28 and the latch mechanism I22 is unfastened and moved radially outward where it will not interfere with the catch I21 and the apron 28. The frame I23 of the latching mechanism may conveniently be provided with an extension I30 which can be screwed to the flanged rim I2 to hold the latching mechanism in this position.

The foregoing preparations having been made, the grinding wheel I44 may be rotated into position above the chuck I I1. The motor.50 is started as previously explained, but the motors I00 and H2 remain inactive because the circuit of relay I44 is held open at the latching mechanism, now in inoperative position. Grinding is accomplished by lowering the grinding wheel on to the work and oscillating the wheel over the work in a manner which will be understood without further explanation.

The invention having been described that which is believed to be new and for which the protection of Letters Patent is desired will be pointed out in the appended claims:

1. In a grinding machine, a base, a vertical column extending upward from said base, a bearing member rotatable and slidable on said column, a grinding wheel and a driving motor therefor mounted on said bearing member, a nut disposed coaxially with said column and fixed to said bearing member, a micrometer screw threaded in said nut, a thrust bearing supporting said screw on said column, a hand wheel rotatably mounted on said bearing member, said hand wheel being disposed in a horizontal plane with its center on the axis of said column, and a driving connection between said hand wheel and said screw, whereby rotation of said hand wheel rotates said screw in said nut to raise or lower said bearing member on said column.

2. In a grinding machine, a base, a vertical column extending upward from said base, a bearing member rotatable and slidable on said c.01- unm, a grinding wheel and a driving motor therefor mounted on said bearing member, a nut disposed coaxially with said column and fixed to said bearing member, a micrometer screw threaded in said nut, a thrust bearing supporting said screw on said column, a hand wheel disposed ooaxially with said column and rotatably supported on said bearing member said hand wheel being of relatively large diameter and accessible irom any point around the machine, a calibrated dial also disposed eoaxially with said column .and fixed to said hand wheel, means responsive to retation of said hand wheel and dial relative to said bearing member for rotating said screw in said nut to raise and lower said bearing member on said column, and an index member fixed relative to said bearing mmnber and cooperating with said dial to indicate thereon the extent 9! such movement.

8. In a grinding a base, .a vertical eolunm extending upward from said base, a bearing member rotatable and slidableon said column. a grinding wheel and a driving motor therefor mounted on said member, a nut disposed eoaxia-lly with said column and fined to said bea.r ing member, a micrometer screw threaded in said nut, a thrust bearing supporting said screw, nut, and bearing member on said column, means rctatably mounted on said bearing member for retoting said screw in said nut to raise and lower said bearing member on said column, said means having a connection with said screw, a circular dial having scale divisions extending around its periphery, said rotating means supporting said dial coaxially with said column for rotation with said screw. and an index member fixed during such rotation and cooperating with the dial to indicate thereon the extent of the movement of the bearing member.

4. In a grinding machine, a base, a vertical column extending upward from said base, a bearing member rotatable and slidableon said column, a grinding wheel and a driving motor therefor mounted .on said bearing member, .a nut disposed coaxially with said column :and fixed to said hear-- ing member, a micrometer screw threaded in said nut, a thrust bearing supporting said screw on said column, a tubular member partly enclosing said screw and rotatably mounted on said bearing member, an operating device and a circular calibrated dial supported on said tubularmember,

said dial being coaxial with said screw and disposed in a horizontal plane, means responsive to rotation of said tubular member by said operating device for rotating said :screw in said nut to raise and lower said bearing member on said column, and an index member relative to which the dial rotates during rotation of the screw, said index member cooperating with the dial to show thereon the extent of movement of the bearing member on said column.

.5. In a grinding machine, a base, a vertical column extending upward from said base, a bearing member rotatable and slidable on said column, a grinding wheel and a driving motor therefor mounted on said bearing member, a nut disposed coaxially with said column and fixed tosaid bearin member, a micrometerscrew threaded in said nut, a thrust bearing supporting said screw on said column, means vfor rotating said bearing member and thegrinding wheel mounted thereon about said column as an axis to br ng the Whi into operative relation to work supported on said base, said nut and screw rotating with said baring member, a hand wheel supported on said bearing member and partaking in such rotation thereof, the supporting means for said hand wheel providing for rotation thereof on the axis of said column independmt of the bearing member, and means responsive to such independent rotation for rotating said screw :in said out to raise and lower said bearing member on said column.

6. In a grinding machine, a horizontal base, a column extending vertically upward from said base, an assembly comm-mug a bearing member rotatable and siidable on said column and havingmounted thereon a grinding wheel and driving motor therefor, and means for raising and lowering said assembly on said column comprising a support on said column and elements including a thrust bearing, a lead screw and a nut threaded thereon disposed in serial relation on the axis of said eolimm. one of said elements resting on said support and another of said elements having a connection with said bearing member, an operating member having a longitudinally sliding but non-rotative connection with said lead screw, and means for rotating said operating member to rotate said lead screw in said nut to raise and lower said bearing member on said column as set forth.

7,. In a grinding machine, a base, a vertical column extending upward from said base, a bearing member rotatably and slidably mounted on said column, a grinding wheel assembly including a grinding wheel and mounted on said bearing member for movement in a circular path above said base, a motor mounted on said bearing member for driving said grmding wheel, a work support mounted on said base in the said path, means having a connection to said assembly and tending to rotate the same to position said grinding wheel at a point angularly spaced from said work support, latching mechanism operating to hold said grinding wheel assembly when the same is rotated about said column to a position above said work support, and means responsive to operation of said latching mechanism to automatically lower said bearing member on said column to .feed the grinding wheel into operative relation to a work piece on said work support.

8. In a grinding machine, a base, a vertical column extending upward i'rom said base, a bearing member rotatably and slidably mounted on said column, a grinding wheel assembly including a grinding wheel and mounted on said bearing member for movement .in .a circular path above said -base,a motor mounted on said bearing member for driving said grinding wheel, a work support mounted on said base at a point in the said path which is angularly spaced from said grinding wheel, means for rotating said work support, and means responsive to rotation of said grinding wheel assembly about said column to a position above said work support for starting the rotation of said work support and for lowering said bearing member to feed the grinding wheel into operative relation to a work piece on said support said last means including electric motors and circuits therefor and a switch actuated by said assembly on arrival at said position to close said circuits.

9. In a grinding machine, a base, a vertical column extending upward from said base, a bearing member rotatably and slldably mounted on said column, a grinding wheel assembly including a grinding wheel and mounted on said bearing member for movement in a circular path above said base, a motor mounted on said bearing member for driving said grinding wheel, a work support mounted on said base in the said path, latching mechanism holding said assembly in a position above said work support when the assembly is rotated to such position, means responsive to such rotation for automatically lowering said bearing member to feed the grinding wheel on to a work piece on said support, means operated in timed relation to the grinding wheel feed for releasing said latching mechanism, and means effective upon such release for rotating said assembly about said column to a position out of alignment with said work support.

10. In a grinding machine, a base, a vertical column extending upward from said base, a bearing member rotatably and slidably mounted on said column, a grinding wheel assembly including a grinding wheel and mounted on said bearing member for movement in a circular path above said base, a motor mounted on said bearing member for driving said grinding wheel, a work support mounted on said base in the said path, and mechanism for sliding said bearing member on said column to move the grinding wheel in and out of operative relation to a work piece on said support, said mechanism including a vertical member slidably mounted in bearings inside said column and extending beneath said base, means including a thrust bearing supporting said bearing member on said vertical member, and mechanism 'beneath said base engaging said vertical member for operating said vertical member for the purpose set forth.

11. In a grinding machine, a base, a vertical column extending upward from said base, a bearing member surrounding and rotatable and slidable on said column, a grinding wheel assembly including a grinding wheel and mounted on said bearing member for movement in a circular path above said base, a motor mounted on said bearing member for driving said grinding wheel, a work support mounted on said base in the said path, a support carrying the weight of said bearing member, means acting against said support and having a connection to said bearing member for adjusting the elevation of said bearing member relative to its said support by sliding it on said column to thereby adjust said grinding wheel relative to a work piece on said work support, mechanism connected to said bearing member through said adjusting means for holding said bearing member oii its said support during movement of the grinding wheel to a position above said work support, and means for operating said mechanism to lower said bearing member on to its said support to effect a desired grinding operation on said work piece.

12. In a grinding machine, a base, a vertical column extending upward from said base, a grinding wheel assembly comprising a grinding wheel and a driving motor therefor, said assembly having a bearing on said column providing for rotative and sliding movement of the assembly on said column, a work support on said base in the path of said grinding wheel when the same is rotated about said column, mechanism for raising and lowering said assembly on said column, means responsive to the grinding wheel being positioned above said work support for operating said mechanism to lower said assembly on said column and to raise the same after the lapse of a predetermined time interval to cause the grinding wheel to remove material from a Work piece on said support, said means including a motor for driving said mechanism and motor starting means operated by a part of said assembly when said grinding wheel arrives in position above said work support, and means interposed between said mechanism and said assembly for preadjusting the elevation of said assembly relative to said mechanism in accordance with the depth of material to be removed.

13. In a grinding machine, a base, a vertical column extending upward from said base, a grinding wheel assembly comprising a, grinding .wheel and a driving motor therefor, said assembly having a bearing on said column providing for rotative and sliding movement of the assembly on said column, a work support on said base in the path of said grinding wheel when the same is rotated about said column, mechanism including a rotatable cam holding said assembly in an elevated position to permit the grinding wheel to be rotated about said column to a position above said work support, means responsive to such rotation for rotating said cam to lower said assembly on said column to bring the grinding wheel into engagement with a work piece on said work support and grind the same, and means independent of said cam supporting said assembly during the final stage of the grinding operation.

14. In a grinding machine, a base, a vertical column extending upward from said base, a grinding wheel assembly comprising a grinding wheel and a driving motor therefor, said assembly having a bearing on said column providing for rotative and sliding movement of the assembly on said column, a work support on said base in the path of said grinding wheel when the same is rotated about said column, automatic feed mechanism having a connection to said assembly for raising and lowering said assembly on said column, said mechanism normally holding said assembly in raised position to permit said grinding wheel to be rotated about said column to a position above said work support, means including a device actuated by said rotation for operating said feed mechanism through a cycle of predetermined duration to perform a grinding operation on a work piece on said work support by lowering and then raising said assembly, and means independent of said feed mechanism supporting said grinding wheel at a fixed distance above said work piece during the final stage of said grinding operation.

15. A grinding machine as claimed in claim 14, characterized by the provision of a cam forming part of said feed mechanism, said cam having a dwell section for supporting the assembly during rotation thereof to position above the work sup port, a rapid feed section to start the grinding operation, and a slow feed section to continue the grinding operation up to the final stage.

16. In a grinding machine, a base, a vertical column extending upward from said base, a grinding wheel assembly comprising a grinding wheel and a driving motor therefor, said assembly having a bearing on said column providing for rotative and sliding movement of the assembly on said column, adjustable means supporting the weight of said assembly to control said sliding movement, a Work support on said base in the path of said grinding wheel when the same is rotated about said column, spring means nor mally maintaining said grinding wheel assembly in an inoperative position relative to said work support, a stop determining said position, means locking the grinding wheel assembly in operative position above said work support when rotated in such operative position, and automatic control means connected with and adapted to operate said adjustable supporting means for lowering and raising the grinding wheel to perform a grinding operation on a work piece on said support, said control means including means for releasing said locking means upon the completion of said grinding operation.

17. In a grinding machine, a base, a vertical column extending upward from said base, a bearing member rotatably and slidably mounted on said column, a grinding wheel mounted on said bearing member for rotation on a vertical axis spaced from said column, said wheel being movable in a circular path above said base by rotation oi said bearing member about said column, means sustaining the weight of said bearing member during rotation thereof about said column, said means comprising a nut disposed coaxially with said column and fixed to said bearing member, a micrometer screw threaded in said nut and a thrust bearing disposed between said screw and a support connected to said base, an operating device for rotating said screw in said nut to raise and lower said bearing member on said column, said device being mounted on and partaking in the movements of said bearing member, the mounting means for said device comprising interengaging bearing elements coaxial with and surrounding said screw and providing for rotation of said device relative to said bearing member, and a connection between said device and said screw which permits the device to move axially of said screw while rotating the same.

18. In a grinding machine, a base, a vertical column extending upward from said base, a hearing member rotatably and slidably mounted on said column, a grinding wheel assembly includ ing a grinding wheel and mounted on said bearing member for movement in a circular path above said base, a motor mounted on said bearing member for driving said grinding wheel, means tending to maintain said assembly at a normal position in said path, a work support mounted on said base at a different position in said path, means including a second motor for lowering said bearing member on said column, a third motor for rotating said work support, electrical circuits for said motors, means for closing the circuit of said first motor, and switching means actuated responsive to rotation of said assembly about said column from said normal position to a position above said work support to close the circuits of the said second and third motors, whereby the work support is rotated and the grinding wheel is fed on to a work piece on said support.

19. In a grinding machine, a base, a vertical column extending upward from said base, a bearing member rotatably and slidably mounted on said column, a grinding wheel assembly including a grinding wheel and mounted on said bearing member for movement in a circular path above said base, a motor mounted on said bearing member and having a driving connection to said grinding wheel, means having a connection to said assembly and tending to rotate the grinding wheel to a normal position in said path, latching mechanism operative to hold said assembly when the same is rotated to a position above a work piece supported on said base, automatic mechanism operating to cause said grinding wheel to perform a predetermined grinding operation on said work piece by lowering and raising said bear- 16 ing member on said column, and means may ing to release said latching mechanism upon the completion or said grinding operation.

20. In a grinding machine, a base, a vertical column extending upward from said base, a baring member rotatably and slidably mounted on said column, a grinding wheel assembly including a grinding wheel and mounted on said hearing member for movement in a circular path above said base, a motor mounted on said hear ing member and having a driving connection to said grinding wheel, means having a connection to said assembly and tending to rotate the grinding wheel to a normal position in mid path. iltdling mechanism operative to hold said assembly when the same is rotated to a position above a work piece supported on said base, and mom nism for sliding said hearing member on mid column to move said grinding wheel in and all of operative relation to said work piece. mid mechanism including a lever pivoted on said base. a cam operatively engaging one arm of said lover. and a connection between the other arm of mid lever and said bearing member.

21. A grinding machine as claimed in claim 3.. wherein the connection between the lever aland bearing member includes mechanism opera, tive to adjust the elevation ot the grinding Ilmd prior to starting the grinding operation.

22. In a grinding machine, a base, a vertical column extending upward from said base and having a finished external bearing surface, a bearing member surrounding said column and rotatably and slidably engaging said bearing surface, a grinding wheel and a driving motor therefor mounted on said bearing member, means comprising a thrust bearing, 0. microneter screw coaxial with said column and a nut threaded on said screw supporting said hearing member, said nut being fixed to said bearing member, an adjusting device, bearing means supporting said device on said bearing member for rotation therewith when the bearing member is rotated on said thrust bearing, said bearing means providing for rotation of said device independent 01' said bearing member, and a driving connection between said device and screw to rotate the screw in said nut to raise and lower the bearing member on said column.

23. In a grinding machine, a base, a vertical column extending upward from said base, a bearing member rotatably and slidably mounted on said column, a grinding wheel assembly including a grinding wheel and mounted on said bearing member for movement in a circular path above said base, a motor mounted on said bearing member for driving said grinding wheel, a work support mounted on said base in the said path, means including a rotatable cam for lowering and raising said bearing member on said column, said means also including a device operated by said cam and having an operative connection to said bearing member, a second motor for rotating said cam, a circuit including said second motor and a switch actuated to complete said circuit by movement of said grinding wheel assembly to a position above said work support, whereby said grinding wheel is fed on to a work piece on said support and then lifted therefrom by rotation of said cam, and means operated by said second motor and efl'ective upon a complete rotation of said cam to open said circuit to stop said second motor.